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SomMeri / less4j

Less language is an extension of css and less4j compiles it into regular css. Less adds several dynamic features into css: variables, expressions, nested rules, and so on. Less was designed to be compatible with css and any correct css file is also correct less file.
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Issue with mixin evaluation #275

Closed twhoff closed 9 years ago

twhoff commented 9 years ago

Description

Again using the for-loop logic as an example, this code should compile and run but doesn't:

    @list: one, two, three;
    @number: 2;

    .for(@i, @n) {
        should-get-executed: and-did;
        .-each(@i)
    }
    .for(@n)     when (isnumber(@n)) {
        .for(1, @n)
    }
    .for(@i, @n) when not (@i = @n)  {
        .for((@i + ((@n - @i) / abs(@n - @i))), @n);
    }
    .for(@array)   when (default()) {
        .for-impl_(length(@array))
    }
    .for-impl_(@i) when (@i > 1)    {.for-impl_((@i - 1))}
    .for-impl_(@i)                  {
        should-not-get-executed: but-did;
        .-each(extract(@array, @i));
    }

   // CALL THE .for() MIXIN HERE WITH ONLY A NUMER FOR THE PARAMETER
    .for(@number); .-each(@val) {
        val: @val;
    }

Error:

Caused by: com.github.sommeri.less4j.Less4jException: Could not compile less. 1 error(s) occurred:
ERROR 35:14 Wrong argument type to function 'extract', expected LIST_EXPRESSION saw number.
 34:     @list: one, two three;
 35:     @number: 2;
 36:

Explanation:

So calling the .for() mixin with a number as the parameter should execute the .for(@n) when (isnumber(@n)) mixin based on pattern matching.

Comment out the following line:

.-each(extract(@array, @i));

You can see in the pattern matching for the .for() mixin is work (ie, it does not output the "should-not-get-executed: but-did;" line) - however it seems it is still evaluating the .-each() mixin in the same scope, which is causing the error.

This compiles fine under the less compiler, so I believe this is a bug.

SomMeri commented 9 years ago

Nice catch, thank you for bug reports.

Simplified example:

    .for(@n)  when (isnumber(@n)) {
        isnumber: true;
    }
    .for(@array) when (default()) {
        should-not-get-executed: but-did;
        //.-each(extract(@array, length(@array))); //un-comment to get error
    }

@list: one, two, three;
.we {   
    @number: 2;
    .for(@number); 
    .-each(@val) {
        val: @val;
    }
}

It is trying to compile .for(@array) despite it not being in output.